In the past, for the purpose of improving the fuel efficiency etc., there has been known a control system of an internal combustion engine suspending the supply of fuel to the internal combustion engine, that is, executing a fuel cut, when it is judged that the vehicle is in a decelerating state (for example, engine braking state) and the supply of fuel to the internal combustion engine mounted in that vehicle is not necessary.
Further, in such a control system of an internal combustion engine, while the fuel cut is in progress, air is prevented from flowing into the catalyst provided in the exhaust system of the internal combustion engine to prevent the catalyst from entering a state of excess oxygen and to suppress deterioration of the catalyst (for example, Japanese Patent Publication (A) No. 2001-182570).